1. Field
The present invention relates to improved photoelectric conversion device to convert optical information as optical intensity and wavelength and so on, and an optical image, into current, charge, voltage, or electric information including digital data, as well as to photoelectric conversion cells, photoelectric converter arrays comprised of the photoelectric conversion cells as the photoelectric conversion device and imaging devices incorporating such an array.
2. Background of the Related Art
A photoelectric conversion device using a photodiode (for example, CMOS image sensors), accumulates electric charges generated (converted) from incident light in a junction capacitance of photodiodes, and takes the electric charge out as electric signals.
However, when a strong light strikes the photodiode, and therefore the converted charge exceeds the amount of charge that can be accumulated in the junction capacitance, a dynamic range of incident light that can be detected is limited.
For example, shooting a plurality of images by changing the time irradiated with light or the time for accumulating the electric charges generated (converted) by light and synthesizing the image shots, is known as a technique for obtaining an image that is not saturated from weak light/strong light (that is, techniques for expanding the dynamic range).
Further, there is a technique to speed up the operation of the photoelectric conversion device for converting incident light into an electric signal.
The photoelectric conversion device includes a phototransistor having an amplifying function, a recharging switch connected to the phototransistor, and a reading switch connected to the phototransistor. By the recharging switch, the phototransistor is connected to an output terminal during one or more clock times after reading (that is, the recharging switch has reset function of the photoelectric conversion device). An electrode of the read switch is connected to the phototransistor, and another electrode is connected to the output terminal. The electric signal is output from the output terminal. In this case, the above configuration removes an after-image and therefore a high-speed operation of the photoelectric conversion device can be provided.